The build-up of condensate moisture has long been a problem in an aircraft fuselage wall or shell forming the primary load-bearing wall structure of the aircraft airframe. Due to the moisture released into the air by the passengers' breath and the like and the natural atmospheric humidity in the cabin air in the enclosed aircraft cabin, and due to the cold temperatures prevailing outside of the aircraft during high altitude flight, the moist interior air that permeates into the structure of the aircraft fuselage shell wall reaches components at or below the dew point temperature for this moist air. As a result, the moisture condenses, and the condensate water tends to accumulate in the wall, unless special provisions are made for the removal of this condensate water.
It has been known to use double-walled composite core structures or structural components having a synthetic (e.g. polymeric) core element enclosed in cover layers of aluminum, fiber-reinforced composite material, or the like, for secondary structures in aircraft. An example of such double-walled composite structures are so-called Nomex honeycomb structures. However, such structural components have always only been used as secondary components, and have not been used in the primary structure of the airframe, e.g. the aircraft fuselage shell, of an aircraft, for various reasons. Most importantly, the known double-walled composite structures suffer an undesirable moisture uptake in service, whereby the structures accumulate condensed moisture in the substantially sealed core, after moist cabin air permeates into the core through a cover layer of the structure, or through small gaps or mounting holes or the like. The moisture is then trapped inside the double-walled composite structure. Therefore, such conventional composite structural components are not suitable for use in the primary fuselage shell, due to the accentuated condensation problems as discussed in the preceding paragraph. Also, the known double-walled composite structures are rather susceptible to damage and consequently require repair. For example, the aim has been to maintain the enclosed and sealed condition of the composite core element.